1. Field of the Invention
The present invention relates to an automatic document feeder (ADF), and more particularly, to an ADF capable of transferring a document to a region where the document is to be scanned, in a multifunctional device to perform functions of a facsimile, scanner, and printer.
2. Description of the Related Art
An automatic document feeder (ADF) is provided in a multifunctional device having a copying function, such as a copier or a facsimile. By providing an ADF, when a multi-sheet document is to be copied, a document sheet can be automatically fed without repeatedly opening and closing the cover in a copying region so that continuous copying can be done; thus, remarkably reducing copying time.
FIG. 1 is a partial perspective view schematically illustrating the structure of a multifunctional device on which a conventional automatic document feeder (ADF) is mounted, and FIG. 2 is a side cross-sectional view to explain a feeding step performed by the ADF shown in FIG. 1.
Referring to FIGS. 1 and 2, the conventional ADF includes a tray 11, on which documents D to be fed into a multifunctional device 10 are stacked, and a pickup roller 12 which draws out a sheet of document D stacked on the tray 11 to enter the multifunctional device 10. The ADF is employed to feed documents.
As shown in FIG. 2, when the pickup roller 12 is rotated by driving a motor 13, the topmost sheet of a stack of sheets, which contacts the pickup roller 12, on the tray 11 is fed into the multifunctional device 10. Reference numeral 14 denotes a cover to protect the pickup roller 12 and an entrance of the multifunctional device 10 into which the document D is fed. The cover 14 is in a closed state, as shown in FIG. 2, during a printing operation.
Meanwhile, in the above structure, a front end of the document D has to be placed well under the pickup roller 12 when the document D is stacked on the tray 11 so that the document D is smoothly fed into the multifunctional device 10. However, when a document containing too many sheets is stacked on the tray 11, it is difficult to place the front end of the document D under the pickup roller 12. Thus, a document having a maximum of 20 sheets can be stacked on the tray 11 at one time. This causes inconvenience for a user in that the user has to stack documents on the tray 11 several times when the document to be printed has a large number of sheets. In addition, in the above structure, the slant of the tray 11 toward the pickup roller 12 is set as steep as possible such that the documents are smoothly slid under the pickup roller 12. Thus, the height of the multifunctional device 10 becomes larger as much, and a large space to install the multifunctional device 10 is needed, and double feeding of the document occurs.
FIG. 3 is a side cross-sectional view of a feeding apparatus disclosed in Korean Patent Publication No. 2001-58632, and FIG. 4 is an exploded perspective view of a frictional member and a pad holder of FIG. 3.
Referring to FIGS. 3 and 4, the feeding apparatus includes a frame 51 provided on a main body of a printer, a pad holder 60 which is hinge-coupled in an intermediate region of the frame 51 and elastically biased upwardly, a pickup roller 50 which is installed to contact the upper portion of the pad holder 60, and a knock-up plate 80 which is fixed on the frame 51 and supports one end of paper P to contact the pickup roller 50.
The pad holder 60 includes a body 61 at one side of which a hinge-coupling portion 64 is formed, and a saddle portion 62 on which a frictional member 63 is mounted. An insertion hole 75, a support protrusion 74, and a coupling hole 69 are formed in the body 61 of the pad holder 60. The saddle portion 62 includes an insertion protrusion 77, a support groove 76, and a hook 73 in which a hanging jaw 73a is formed. A support plate 78 which supports upper and rear sides of the pad holder 60 through a long hole 65 and fixes the frictional pad 63 and the saddle portion 62 to the body 61, is arranged. In addition, a protrusion 66 is formed at a rear side of the body 61, and an elastic spring 71 is connected to the protrusion 66, such that the pad holder 60 is elastically biased upwardly.
In the feeding apparatus having the above structure, a sheet of a document that contacts the pickup roller 50 by the rotation of the pickup roller 50 is picked-up and fed to a feed path. And, double feeding is prevented by a friction force of the friction pad 63.
In order to replace the frictional pad 63 with another one, a user removes the pickup roller 50 from the printer, and then, presses a protrusion 68 by about 1.5–2.0 mm by hand. Then, the coupling hole 69 is moved to the right sides of FIGS. 3 and 4, and the locked state of the hook 73 hung by the hanging jaw 73a in the coupling hole 69 is released. If the protrusion 68 is continuously pressed, a body of the saddle portion 62 is slid along a slanted surface of a rib 72 and is naturally lifted. Thereafter, the support plate 78 which clips the frictional pad 63, is lifted, and the frictional pad 63 mounted on the saddle portion 62 is removed, and a new frictional pad 63 is mounted on the saddle portion 62 and assembled for use.
However, the structure of the pad holder 60 is complicated. If the support plate 78 is deformed due to long-term use, the frictional pad 63 is not fixedly mounted on the saddle portion 62, and it is not easy for the user to dismantle the pickup roller 50 and replace the frictional pad 63 with another one.